class Dog():
    """一次模拟小狗的简单尝试"""

    def __init__(self,name,age):
        """初始化属性和name和age"""
        self.name = name
        self.age = age

    def sit(self):
        """模拟小狗命令时蹲下"""
        print(self.name.title()+" is now sitting.")

    def roll_over(self):
        """模拟小狗被命令时打滚"""
        print(self.name.title() + " rolled over!")

my_dog = Dog('willie', 6)

print("My dog's name is " + my_dog.name.title() +".")
print("My dog is "+str(my_dog.age) +"years old.")
my_dog.sit()
my_dog.roll_over()
